Vibrating material feeders or conveyors are often used when uniform material feed is desired. For example, when mixing ingredients, a vibrating material feeder for each ingredient is often used. The material fed by each individual feeder must be highly uniform and controlled in order to ensure the proper ratio of ingredients in the mixture. Vibratory material feeders are also used in the manufacture of composite materials including fiber reinforced plastics, metals, ceramics and the like.
When certain materials are used, for example, those susceptible of agglomeration, it is very difficult to maintain uniform material feed without material clumping. This problem is particularly evident when feeding fibrous material.
One solution to the problem of material agglomeration is found in U.S. Pat. No. 3,524,533 wherein vibrating fingers are attached to walls of the material feed tray so as to extend into the interior of the feed tray. However, this approach requires mechanical tuning of the fingers so as to maintain the desired vibration of the fingers, and is not readily adaptable to feeding fibrous materials.
When feeding fibrous materials, for example, chopped fiber glass or carbon or graphite fiber, it is highly desirable to align the individual fibers along the direction of a material feed in order to promote uniform material feed. Use of vibrating fingers within the tray may actually serve to misalign the individual fibers thereby degrading uniform material feed. Thus, use of vibrating fingers attached to the material feed tray may not provide a solution to the problem of feeding fibrous materials at a uniform rate.